The present invention relates to a filter apparatus for separating particles from a liquid.
U.S. Pat. No. 5,601,729 discloses a filter apparatus for separating particles, dirt or chips from a liquid. This apparatus comprises a tank with a feed inlet, a gravitational settling zone and a filtration zone disposed downstream thereof. Two transversely spaced-apart, driven, endless chains extend within the tank and entrain a nonwoven filter web or a filter media strip. This nonwoven filter web or filter media strip completely covers a filtered liquid region of the device. The chains prevent the nonwoven filter web or media strip from lifting off the filtered liquid region and thereby prevent dirt from getting into the filtered liquid region. A drawback of these chains is that they cannot be designed as flat tracks but that the chain links are individual elements with a waisted shape that may have the result that dirt can pass into the filtered liquid region through the chain links.
To prevent the penetration of dirt around the filter media, the prior art proposes to dispose an inflatable tube seal in the critical sealing region to provide an additional lateral seal between the unfiltered liquid region and the filtered liquid region. If the filter media strip must be moved, this seal must be deflated, i.e., at least partly evacuated, so that the filter media strip can slide along underneath the seal. Especially when the filter media strip is moved, however, strong turbulence occurs in the region of the unfiltered liquid and with the result that dirt can be carried into the filtered liquid region. Thus, this prior art has the disadvantage that the lateral seal is only intermittently effective.